How long does a flat roof last?

1The ranges, covering by covering

Start with the general figure. The broadest figure comes from MyBuilder's flat roof guide (updated 21 August 2026): 15 to 30 years. That is the middle of a wide field, and each covering sits somewhere inside it or beyond it.

For torch-on felt, Less (updated March 2026) gives 10 to 20 years, and adds that careful laying can carry felt to 20 years where careless laying may end it inside 10. CORC says well-maintained felt can last 30 years or more. For GRP fibreglass, Less gives 25 to 40 years and CORC says 25 or more.

For EPDM, GreenSpec's expected service life is 20 to 30 years, Less says 30 to 50 and CORC says 50 or more. A safe summary is 20 to 30 years or more.

Treat all of these as typical ranges. A manufacturer's warranty measures something else again, and neither a range nor a warranty promises anything about your roof.

2Why the sources disagree

When one guide says 10 years and another 30 for the same material, the difference usually lies in what each assumes. Some count a roof as finished when the first patch is needed. Others count until it has to be completely replaced. A roof that has been patched twice can be recorded as lasting twelve years by one guide and twenty-five by another.

The author's interest matters too. A trade body or manufacturer may quote what the product can do in ideal conditions, laid by a trained installer on a sound deck. A cost guide quotes what roofers usually find on ordinary houses. Neither is wrong, but they answer different questions.

Quality of installation sits behind most of the spread. Less's comment on felt, with 20 years for a good job against under 10 for a poor one, shows how much weight the workmanship carries. When you read a range, ask what it assumes about the deck, the fall and the laying.

3What shortens a flat roof's life

Standing water is the main enemy. A flat roof is built with a fall towards an outlet; IKO, citing the 2018 edition of BS 6229 (since revised), recommends a finished minimum of 1:80, built from a design fall of 1:40 so tolerance and deflection do not eat it. A sagging deck or a blocked outlet lets water pool, and pools age a covering faster and find any seam.

Other causes are mechanical. Foot traffic, falling branches and the movement of a loose deck wear the surface. Poor detailing at upstands, edges and rooflights is where most failures start, since these are the points where the membrane has to turn up a wall or around a penetration.

Neglect speeds it up. Silt and leaves in gutters and gullies, moss along edges and small splits left alone all let water in. Our page on the disadvantages of EPDM covers how its weak points show, and the page on the EPDM rubber roofing explains the system.

4What helps one last longer

Begin with a sound deck and a proper fall. A new covering laid over wet or rotten boards inherits the problem. A survey of ours checks the deck, the fall, the outlets and the edge details, with photographs of each, so the repair or replacement suits the cause.

Choose a covering that suits the use. A roof people walk on, a roof under overhanging trees and a roof with many penetrations each ask for different things. The flat roof materials page compares the options.

Then keep up with it, because regular upkeep adds years to a flat roof for very little outlay. Clear the outlets, look at the surface after storms and have a small split or lifted edge dealt with quickly. A routine look twice a year costs little against a failed roof. The cost of replacement is in our page on EPDM roof cost, where MyBuilder puts EPDM at a typical UK range of £90 to £130 per m².

5Repair, overlay or replace

A roof at the far end of its range does not always need replacing. A single split, a lifted seam or a failed corner can often be repaired where the rest is sound. Where the covering is tired all over, or the deck beneath is damp, patching only delays the bill.

Age alone is a poor reason either way. A well-laid ten-year-old felt roof can be fine, while a badly detailed three-year-old one may already be failing. We judge by actual condition, send photographs, and suggest the lightest job that does the work, whether that turns out to be a repair or a full replacement.

Once surveyed, you get one total price in writing. If you are weighing a new roof, why houses have flat roofs explains where they suit a building, and the question of when replacement beats repair is covered on our flat roofing page.